Automatic tension sensing apparatus for belt conveyor

ABSTRACT

A sensitive measurement of tension in a belt is provided by movement of a belt carrying pulley mounted on a pivoted arm extending from the pivot to a position beyond the pulley where a calibrated spring permits limited movement of the arm in opposition to belt forces on the pulley. The movement of the arm actuates limit switches which are operatively connected to a take-up pulley mechanism for maintaining the desired tension in the belt.

O Unlted States Patent 1 1 ,675,482 Hewitt 1451 July 11, 1972 s41AUTOMATIC TENSION SENSING 3,538,763 11/1970 Amtsberg =1 a] ..13/1 36 RAPPARATUS FOR BELT CON VEY 2 l a H a a 0R FOREIGN PATENTS ORAPPLICATIONS 7 to enltt, T ad Ohio I 1 J 837,615 6/!960 Great Britain03/144 1 u Gwdyur & Rubber p- 1. 990,8ll 5/!965 Great Britain ..73/|44Akron. Ohio [22] m Oct 14, 1970 Primary Examiner-Charles A. RuehlAttorney-F. W. Brunner and Frederick K. Lacher [21] Appl. No.: 80,636

ABSTRACT [52] U3. Cl. ..73/l44, 198/208 A ma mmmem f tension in a isprovided by [$1 Int. Cl. ..G0ll 5/06 movement of be" carrying ll mounedon a pivoted m M0Wll............................................73/|43,exwndins from the pi to a p i i y d the p y where a calibrated springpermits limited movement of the [56] CM arm in opposition to belt forceson the pulley. The movement UNITED STATES pATEm-S of the arm actuate:limit switches which are operatively connected to a take-up pulleymechanism for maintaining the 2,353,249 7/ I944 Lebourg ..73/l44 desiredtension i the b 2,758,472 8/1956 Bowen, Jr.... ..73/l44 2,826,065 3/1958Glimes............................1.73/l41 AB BClallm, 5 Dnwingfl uresPATENTEDJUL 1 1 m2 SHEET 10F 2 INVENTOR.

JOHN H. HEWITT ATTORNEYS PKTENTEDJIJL 1 1 m2 SHEET 2 BF 2 mm M Ma QINVENTOR. JOHN H. HEWITT ATTORNEYS AUTOMATIC TENSION SENSING APPARATUSFOR BELT CONVEYOR This invention relates generally to a tensionindicating apparatus for belt type conveyors and more particularly to atension sensing apparatus for a passenger conveyor system in which thebelt tension on the slack side of the driving pulley is sensed andautomatic adjustments are made to the belt tension when a need for theseadjustments is indicated by the apparatus.

Passenger conveyor systems of the moving belt type run continuouslyunder varying loads. For example, a conveyor in an airport has periodsof maximum load when planes arearriving or departing and other periodsof minimum load when few or no planes are arriving or departing. Forefficient operation of the conveyor system it is desirable that thetension in the belt be maintained within a certain range so that therewill be sufficient frictional engagement between the drive pulley andthe belt to prevent slippage or creeping of the belt which causesundesirable jerks in the belt movement and also results in abnormal wearof the belt when the tension is not sufficient. n the other hand if thetension is greater than necessary, the strain on the conveyor systemwill lead to abnormal wear and early failure of the belt and other partsof the system.

Spring loaded take-up pulleys or weighted take-up systems have been usedon belt conveyor systems in the past to provide an adjustment for thevarying loads on a conveyor to change the tension in the slack side ofthe belt; however, none of these devices have been capable of adjustingthe tension of the belt within specific limits through an independentmeasuring and indicating apparatus which is not part of the take-upadjusting apparatus. The prior devices have also operated with heavyduty weights or springs and therefore have not had the sensitivity tomeasure relatively small changes in tension and make adjustmentsaccordingly.

It is therefore the principal object of this invention to provide atension measuring means for a belt conveyor with a tension measuringpulley for carrying large belt loads and a leverage means for reducingthe measured load.

Another object of the invention is to provide for mounting the pulley onan arm which is pivoted for rotation in response to changes in tensionin the belt passing around the pulley.

A further object of this invention is to provide a calibrated spring forengagement with the pulley arm assembly whereby deflection of the springindicates the tension in the belt passing around the pulley.

A still further object is to provide for positioning the pulley and thespring relative to the pivot of the arm so that maximum sensitivity isprovided with a relatively small spring.

Other objects and advantages of the present invention will becomeapparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter fully described andparticularly pointed out in the claims, the following description andthe annexed drawings setting forth in detail a certain illustrativeembodiment of the invention. this being indicative, however, of but oneof the various ways in which the principles of the invention may beemployed.

ln the drawings:

FIG. I is a schematic side elevational view of a passenger conveyorsystem including a preferred form of tension sensing apparatusconstructed in accordance with this invention.

FIG. 2 is an enlarged side elevational view of the tension sensingapparatus and take-up mechanism of FIG. 1.

FIG. 3 is a cross sectional view taken along the plane of line 33 ofFIG. 2;

FIG. 4 is a plan view taken along the plane of line 4-4 of FIG. 2.

FIG. is an end view in elevation of the take-up apparatus taken alongthe plane of line 5-5 of FIG. 2.

Referring now in detail to the drawings and first especially to FIG. 1,there is shown a belt tension indicating apparatus 1 in a conveyorsystem in which an endless belt 2 for conveying passengers or objectspasses around a tension measuring pulley 3 of the belt tensionindicating apparatus and then around a take-up pulley 4 responsive tothe belt tension for adjustment thereof.

In the embodiment shown, the conveyor is of the type used for carryingpassengers from one level to another level and the belt 2 has an upperrun 5 extending from a lower terminal pulley 6 to an upper terminalpulley 7 with rollers 8 supporting the belt at the convex portionthereof. Other rollers not shown may be provided along the edges of thebelt 2 to support the upper run 5 at other positions between the lowerterminal pul ley 6 and upper terminal pulley 7.

Although conveyors of this type may be reversible, the conveyor shown isin the condition where the entrance end 9 is at the lower terminalpulley 6 and the exit end 13 is at the upper terminal pulley 7. Thelanding platforms l4 and floating combs 15 may be provided at theentrance end 9 and exit end 13. Balustrades, not shown, may also beprovided at each side of the belt 2 and have handrails movable at thesame speed as the belt.

A lower run 16 of the belt 2 extends from the upper terminal pulley 7 tothe lower terminal pulley 6 and may pass over guide rollers 17 at theconvex portion of the lower run or other portions where the belt needsto be directed. A main drive pulley 18 is located intermediate the upperterminal pulley 7 and the tension measuring pulley 3 and may beconnected to a motor or other means for turning the pulley in theclockwise direction as shown by the arrow. An idler pulley 19 adjacentthe drive pulley 18 carries the lower run 16 from the guide rollers 17to the main drive pulley 18.

Between the drive pulley l8 and the take-up pulley 4 of the lower run 16is an upper reach 20 and a lower reach 21 which are in substantiallyparallel relationship. An arm member 22 extends generally parallel andbetween the upper reach 20 and lower reach 2! to a position spaced fromthe tension measuring pulley 3. The arm member 22 has arms 26 and 27 atthe sides and are connected by transverse members such as angles 28 and29. Each of the arms 26 and 27 are pivotally supported by brackets 32and 33 having pins 34 and 35 extending through the arms and brackets ina direction parallel to the axis of the tension measuring pulley 3. Thebrackets 32 and 33 are fastened as by welding to structural members 36and 37 of a supporting structure 38 for the belt tension indicatingapparatus l and a tension adjusting apparatus 39.

Pillow blocks 40 and 41 are fastened to the arms 26 and 27 as by bolts44 and contain journals for carrying a shaft 45 of the tension measuringpulley 3. As shown in the drawings and especially FIGS. l, 2 and 3, theaxis of the shaft 45 of the tension measuring pulley 3 is above the axisof the pins 34 and 35 pivotally mounting the arms 26 and 27 on thebrackets 32 and 33 so that the tension in the upper reach 20 and lowerreach 21 of the belt 3 tends to rotate the arm member 22 in a clockwisedirection around the pins 34 and 35.

The arms 26 and 27 extend between the upper reach 20 and lower reach 21a substantial distance from the pivotal connection at pins 34 and 35where a spring means such as coil springs 46 and 47 engage the armmember 22 to resist clockwise turning of the member as a result of thebelt tension. The springs 46 and 47 may engage the arms 26 and 27 atpositions which are at least nine times the distance between the pins 34and 35 and the axis of the shaft 45 of the tension measuring pulley 3.The coil springs 46 and 47 may be of steel and calibrated for a desireddeflection at certain loading. Hanging brackets 48 and 49 are mounted onupper structural members 55 and 56 and have upperwardly projecting pins57 and 58 over which the coil springs 46 and 47 are placed and supportedin operating position.

In order to measure the movement of the arm member 22 resulting from thechange in tension in the belt upper reach 20 and lower reach 21 actingon the tension measuring pulley 3 and deflecting the coil springs 46 and47. a sensing means such as a limit switch 59 is mounted on the upperstructural member 55 and has an arm 60 extending outward into engagementwith the surface of arm 26. This arm 60 may be spring loaded to maintainengagement with the arm 26 of the arm member 22 and is preferably spacedfrom the pivotal connection at pins 34 and 35 to provide for greaterthrow of the arm member 22 than at the portions closer to the pivotalconnection.

As shown in the drawings, the take-up pulley 4 is mounted along the beltpath of the lower run 16 between the tension measuring pulley 3 and thelower terminal pulley 6. A shaft 61 of the take-up pulley 4 is supportedat either end by crossheads 62 and 63 which are supported on slides 64and 65 mounted at spaced-apart positions on intermediate structuralmembers 66 and 67 for movement of the crossheads and the take-up pulleytoward or away from the tension measuring pulley 3.

Threaded rods 68 and 69 are fastened to the crossheads 62 and 63 andextend in a direction away from the tension measuring pulley 3 to theend of the supporting structure 38 and to a drive mechanism 70 mountedon the supporting structure by brackets 71 and 72. A drive motor 76which may be reversible is connected to a drive shaft 77 through asuitable transmission and rotates sprockets 79 and 80 which areconnected to drive sprockets 81 and 82 by chains 83 and 84. The drivesprockets 81 and 82 are threaded on the rods 68 and 69 and journaled inthe brackets 71 and 72 to permit rotation but restrain movement of thesprockets in the direction of the crossheads 62 and 63. It can be seenthat by actuating the motor 76 and turning the sprockets 81 and 82, therods 68 and 69 may be moved causing the crossheads 62 and 63 to move andthereby increase or decrease the tension in the lower run l6ofthe belt2.

Suitable connections are provided between the limit switch 59 and themotor 76 of a type well known in the art so that when the arm member 22moves in a clockwise direction, as shown in FIG. 2, a predeterminedamount as in the case of increased belt tension caused by an increasedload on the upper run of the belt 2, this will actuate the motor 76 toturn the sprockets 81 and 82 in a direction to permit the crossheads 62and 63 to move towards the tension measuring pulley 3 and thereby movethe take-up pulley 4 in that direction releasing the tension in thebelt. As the tension in the belt is released. the calibrated springs 46and 47 will urge the arm member 22 in a counterclockwise directioncausing the arm 60 of the limit switch 59 to be lifted and at apredetermined position to actuate the motor 76 to turn the sprockets 81and 82 in the opposite direction to move the crossheads 62 and 63 awayfrom the tension measuring pulley 3 and thereby move the take-up pulley4 in the same direction increasing the tension in the belt 2. It isunderstood that in a range between the two positions set forth above,the motor 76 will not be actuated and the crossheads 62 and 63 willremain in a stationary position holding the take-up pulley 4 in thatposition where the belt tension is in the range desired for operation.

Although the take-up pulley 4 is shown in this embodiment actuated bythreaded rods 68 and 69 through a motor 76, it is to be understood thatother types of take-up mechanisms may be used with the belt tensionindicating apparatus 1 of this invention. For example, with a horizontalmoving walkway the take-up pulley may be mounted on a movable carriagecarrying nuts at each end through which stationary rotatable rods arethreaded. The rods are mounted in bearings and turned by a drivemechanism to move the nuts and thereby adjust the position of thecarriage and the take-up pulley. It is also understood that even thoughthe present invention is primarily designed for passenger conveyors, itcan be used for other conveyors and belt systems if desired.

While certain representative embodiments and details have been shown forthe purpose of illustrating the invention. it will be apparent to thoseskilled in the art that various changes and modifications may be madetherein without departing from the spirit or scope of the invention.

lclaim:

l. A belt tension indicating apparatus comprising a pulley, pulley meansat one side of said pulley for carrying reaches of the belt to and fromsaid pulley and directin the belt tension forces on said pulley in t edlrectlon of ear pulley means, a

swingable supporting member on which said pulley is mounted extending inthe direction of said pulley means between the reaches of the belt.spring means in engagement with said swingable supporting member andwith a fixed body for deflection in response to belt tension forcesexerted against said pulley in the direction of said pulley means andsensing means responsive to swinging movement of said support member forindicating the tension in said belt.

2. A belt tension indicating apparatus according to claim 1 wherein saidsupporting member comprises an arm member having a pivotal mounting at aposition adjacent the axis of said pulley and spaced from said springmeans.

3. A belt tension indicating apparatus according to claim 2 wherein saidpulley is mounted on said arm with the axis of said pulley at a positionwhich is closer to said pivotal mounting of said arm member than theposition where said spring means engages said arm member to minimize thesize of the spring means required to oppose the belt tension forces onsaid pulley means.

4. A belt tension indicating apparatus according to claim 3 wherein saidsensing means engages said arm member at a position spaced from saidpivotal mounting of said arm member whereby the movement of said armmember at said sensing means is sufficient to measure the deflection ofsaid spring means corresponding to a predetermined range of belttensions.

5. A belt tension indicating apparatus according to claim 4 wherein saidspring means is a coil spring deflected in compression by tension in thebelt.

6. A belt tension indicating apparatus according to claim 2 wherein theaxis of said pulley is spaced from said arm member in a direction normalto said arm member and said spring means is spaced from said pivotalmounting in a direction parallel to said arm member.

7. A tension indicating apparatus according to claim 6 wherein thedistance between said pivotal mounting of said arm member and theposition where said spring means engages said arm member is over ninetimes the distance between said pivotal mounting and the axis of saidpulley.

8. A belt tension indicating apparatus according to claim 2 wherein saidarm member has two arms extending alongside the edges of the belt andsaid spring means includes a spring between each of said arms and saidfixed body at the edges of the belt.

* t i i l

1. A belt tension indicating apparatus comprising a pulley, pulley means at one side of said pulley for carrying reaches of the belt to and from said pulley and directing the belt tension forces on said pulley in the direction of said pulley means, a swingable supporting member on which said pulley is mounted extending in the direction of said pulley means between the reaches of the belt, spring means in engagement with said swingable supporting member and with a fixed body for deflection in response to belt tension forces exerted against said pulley in the direction of said pulley means and sensing means responsive to swinging movement of said supporting member for indicating the tension in said belt.
 2. A belt tension indicating apparatus according to claim 1 wherein said supporting member comprises an arm member having a pivotal mounting at a position adjacent the axis of said pulley and spaced from said spring means.
 3. A belt tension indicating apparatus according to claim 2 wherein said pulley is mounted on said arm with the axis of said pulley at a position which is closer to said pivotal mounting of said arm member than the position where said spring means engages said arm member to minimize the size of the spring means required to oppose the belt tension forces on said pulley means.
 4. A belt tension indicating apparatus according to claim 3 wherein said sensing means engages said arm member at a position spaced from said pivotal mounting of said arm member whereby the movement of said arm member at said sensing means is sufficient to measure the deflection of said spring means corresponding to a predetermined range of belt tensions.
 5. A belt tension indicating apparatus according to claim 4 wherein said spring means is a coil spring deflected in compression by tension in the belt.
 6. A belt tension indicating apparatus according to claim 2 wherein the axis of said pulley is spaced from said arm member in a direction normal to said arm member and said spring means is spaced from said pivotal mounting in a direction parallel to said arm member.
 7. A tension indicating apparatus according to claim 6 wherein the distance between said pivotal mounting of said arm member and the position where said spring means engages said arm member is over nine times the distance between said pivotal mounting and the axis of said pulley.
 8. A belt tension indicating apparatus according to claim 2 wherein said arm member has two arms extending alongside the edges of the belt and said spring means includes a spring between each of said arms and said fixed body at the edges of the belt. 